Light measuring device

ABSTRACT

The present disclosure relates to a universally applicable light measuring device, especially photometer, which comprises a main measuring device, e.g., an exposure meter, and a plurality of easily exchangeable auxiliary measuring devices or adapters which, when individually attached to the main measuring device, form therewith new unitary devices, as to outer appearance and function. All adapters have identical bottom portions with two hook-like extensions to be received in corresponding recesses in the main measuring device. One of the extensions is resiliently journalled and may be displaced by a push button for disconnecting the adapter from the main device. Various new adapters are proposed, as for instance, an adapter for reducing the measuring angle, a dark room adapter, an adapter for determining the exposure time when taking micro-photographs, a focusing screen scanner, an adapter which transforms the main measuring device into an illumination meter, an adapter for determining the &#39;&#39;&#39;&#39;color temperature&#39;&#39;&#39;&#39; when taking color photographs, and an adapter for making densitometric measurements.

United States Patent [15] 3,697,179 Piaifenberger et al. 1 Oct. 10, 1972[54] LIGHT MEASURING DEVICE FOREIGN PATENTS OR APPLICATIONS [72]inventors: Erwin Plaffenberger; Hans 156,695 8/1939 Austria ..356/224Far-sterling, both of Erlangen, Ger- 356,503 2/ 1938 Italy ..356/275many OTHER PUBLICATIONS [73] Assignee: P. Gossen 8: Co. G.m.b.H.,Erlangen, Bavaria, Germany [22] Filed: Jan. 18, 1971 [21] Appl. No.:107,584

Related [1.8. Application Data [63] Continuation of Ser. No. 631,947,April 19,

1967, abandoned.

[30] Foreign Application Priority Data Oct. 29, 1966 Germany ..P 15 47309.3

[52] US. Cl. ..356/73, 356/220, 356/224, 356/225 [51] Int. Cl. ..G01n21/00, Golj 1/42 I581 Field of Search ..356/221-226, 73; 24/230 A-230 M[56] References Cited UNlTED STATES PATENTS 2,982,174 5/1961 Crandell..356/73 3,421,821 1/1969 Alessi ..356/186 3,237,264 3/1966 Turolla..24/230 A-M 2,584,440 2/1952 Fogle ..356/224 2,585,245 2/1952 Harrison..356/73 2,995,975 8/1961 Balchunas et al ..356/222 X 3,360,656 12/1967Kinnard ..356/73 X Gossen, PSA J., December 1966, pp. 10- 1 1 PrimaryExaminer-Ronald L. Wibert Assistant Examiner-Warren A. SklapAttorneyNo1te & Nolte ABSTRACT The present disclosure relates to auniversally applicable light measuring device, especially photometer,which comprises a main measuring device, e.g., an exposure meter, and aplurality of easily exchangeable auxiliary measuring devices or adapterswhich, when individually attached to the main measuring device, formtherewith new unitary devices, as to outer appearance and function. Alladapters have identical bottom portions with two hook-like extensions tobe received in corresponding recesses in the main measuring device. Oneof the extensions is resiliently journalled and may be displaced by apush button for disconnecting the adapter from the main device.

for determining the color temperature" when taking color photographs,and an adapter for making densitometric measurements.

3 Claims, 11 DrawingFigures P'ATENTEuum 10 m2 l r ylllflllllllll/ Fig. 2

3.697.179 SHEET 1 UF 4 39 I /IO M15 1}] III 5 llr I60 2 "9 -2 9 Q 3INVENTORS ERWIN PEAFFENBERGER HANS FORSTERLING ATTORNEYS PATENTED 10I973 3.697.179

sum 2 0r 4 INVENTORS ERWIN PFAFFENBER R HANS FORSTERLI ATTORNEYSPATENTEDBBT 10 I972 SHEET 3 OF 4 FIG. 8

INVENTORS ERWIN PFAfFEN BERGER HANS FORSTERLING ATTORNEYS PATENTEU I9733.697.179

SHEET '4 1F 4 INVENTORS ERWIN PFAFFENBERGER HANS FORSTERLI NG ATTORNEYSLIGHT MEASURING DEVICE This application is a continuation of Ser. No.631,947, filed Apr. 19, I967, now abandoned.

SUMMARY OF THE INVENTION The present invention relates to a universallyapplicable photometer, especially for carrying out phototechnicalmeasurements. It comprises a main measuring device and a plurality ofadapters or auxiliary measuring devices, which can be connected to themain or basic device by identical means in such a way that a new andunitary device as to appearance and function is created while permittingeasy exchange. The main device by itself or in combination with thevarious adapters may be used to carry out a number of differentphotometric measurements.

In order to solve the problems involved as to appearance and function,it was necessary to design the adapters to be combined with the maindevice so that upon assembly a unitary device is produced. To this endall adapters are provided with the same connecting device or arrangementwhich permits exchange in a very simple manner. The connecting device isnot apparent at the main or basic device since the latter is to be usedalso without the adapters. In addition, care had to be taken that adiffusor which is non-detachably but displaceably connected to the maindevice, is located outside the path of the rays, to be measured duringuse of the adapters, bodily and functionally. Moreover, the individualelements of the combination have to be adapted to the physicalproperties of the main device, which operates as an exposure meter.

It is an object of the present invention to provide a composite lightmeasuring device, especially a photometer, which is universallyapplicable for carrying out a large number of photometric measurements.

It is another object of the present invention to provide a lightmeasuring device as set forth above which comprises a main measuringdevice and a plurality of exchangeable auxiliary measuring devices whichcan easily be connected to and detached from the main measuring device.

Still another object consists in the provision of cooperating means forconnecting the auxiliary measuring devices, one at a time, to the mainmeasuring device.

According to still another object of this invention, novel auxiliarymeasuring devices or adapters are proposed for reducing the measuringangle of an objective, for use in the dark room while makingenlargements, for making micro-phot, for scanning focussing screenimages, for determining the color temperature" of objects, or forcarrying out densitometric measurements, and others.

The present invention is illustrated by way of example in the followingdrawings, in which:

FIG. I is a front view, partly in section, of an exposure meter with anadapter;

FIG. 2 is a cross section of an adapter for reducing the measuring angleof the exposure meter, and taken along the line 2 2 of FIG. 3',

FIG. 3 is a top view of the adapter of FIG. 2;

FIG. 4 is a light conductor for use in one of the adapters according tothe present invention;

FIG. Sis a cross section through an adapter for use in the dark room;

FIG. 6 is a section taken along the line 6 6 ofFlG.5,attwicethescaIeofFlG.$;

FIG. 7isacrosssectionthroughanadapterforuse in the making of micro;

FIG. 8 illustrates a cross section through a focussing screen scanneraccording to the present invention;

FIG. 9 shows an adapter which, when combined with the exposure meter ofFIG. 1, forms a luxmeter;

FIG. 10 shows a crow section of an adapter for determining the "colortemperature" of color photos p aan FIG. 11 represents a cross section ofan adapter for carrying out densitornetric measurements.

For connection to the main measuring device, all adapters have anidentical bottom with a stationary hook-like extension and a resilientmovable nose portion adapted to engage recesses at the top of theexposure meter. The resilient nose portion may be de by a key accessiblefrom the outside and, therefore, permits a fast exchange. Furthermore, arecess for the above-mentioned diffuser is provided which, uponattachment of an adapter is displaced in such a way that it occupies aposition in this recess.

The connecting device proper, according to FIG. 1, comprises anextension 2 in the form ofa hook and arranged at the bottom 1b ofhousing I of the adapter. Extension 2 slides into a recess 4 at the topof the main device 3 when the adapter is attached to the latter. Aresilient nose 5 with a key 6 adapted to be actuated by hand from theoutside is arranged opposite extension 2. Nose 5 is resiliently held inhousing I of the adapter and is caught in a second recess 7 of maindevice 3. In this way, the main device and the adapter are fixedlyconnected to each other. For purposes of disconnecting the adapter fromthe main device, key 6 is depresed whereby the adapter may easily bedetached. Prior to the connection of the adapters to the main device thedifiuser 3a is slidably displaced so that it is located below thedepression in of the adapter and is received therein.

The main device 3 proper, i.e., the exposure meter in the embodimentshown, has the customary measuring angle of approximately 30, in otherwords, is somewhat smaller than the picture angle of an objective ofnormal focal distance. In order to be able to measure with smallermexuring angles which correspond to the picture angles of ordinaryteleobjectives, as, for instance, with an angle of IS or the path of therays has to be reduced to the desired value by means of an adapter and avariable aperture of a diaphragm.

The structure of this adapter for reducing the measuring angle has to besuch that a compact unit and light losses as small as possible areobtained. The optical structure comprises three parts, viz, two convexor collecting lenses and a variable or adjustable diaphragm which isarranged between the two lenses close to the lens on the exit side. Asan optimum solution, the lens on the entrance side is so designed thatit produces an image of the distant objects in the plane of thediaphragm. The focal distance f of this lens and the aperture of thediaphragm with the radius a are so dimemioned that the desiredacceptance angle a satisfies the condition;

tana =a/f,

The focal distance of the lens on the exit side is so selected that theopening or aperture of the lens on the entrance side appears on areduced scale on a photoconductive cell or photoresistance of the mainor basic measuring device. This image is produced, according to FIG. 1,with the cooperation of the lens 3b on the entrance side, which isanyhow present in the main device. The variable diaphragm is formed by aslide with two different size diaphragm apertures. Furthermore, anoptical view finder is incorporated in the housing of the measuringangle reducing adapter, since it is very difficult without this aid tosight the object to be measured accurately when small measuring anglesare involved.

The just-mentioned adapter for reducing the measuring angle is shown inFIG. 2 in longitudinal section and in FIG. 3 in top view. It comprises ahousing 8 with a viewing opening 9 for the view finder, which is coveredby a small glass plate 10. Two annular, colored grooves llr and llg areground into this plate and indicate in the view finder the limits of therespective measuring angle in color (red and green). Two lenses l2 and13 are arranged on that side which faces the object being measured. Lens12 in combination with a deviating mirror 14 serves as finder andproduces images of distant objects on the small glass plate 10, whereaslens 13 and lens 15, in combination with disc diaphragm 16 arrangedadjacent lens 15, serve as actual measuring angle limiting means.Diaphragm 16 has two apertures corresponding to the measuring angles 15and 75 and is adjustable from the outside by means of a slide 16adiagrammatically illustrated in FIGS. 2 and 3. When reading the exposurevalues on the main device and when adjusting the calculating ring 3gaccording to FIG. 1, a reading mark 3e or 3f which is offset with regardto the main reading mark M is to be used because of the light loss inview of the reduction of the measuring angle to 15 and 7.5 respectively.The symbols corresponding to these marks have been transferred to slide160 and are visible in the corresponding position of the latter (seeFIG. 3). It is, of course, to be understood that instead of the twomeasuring angles of l5 and 7.5, selected by way of example also three ormore angles with different values may be accommodated in the diaphragm16.

The present invention also proposes a new adapter which may be employedas dark room adapter for determining the exposure period required whenmaking enlargements. With such a device it is necessary to deviate thelight falling on the plane of the paper by 90 into the horizontal lightentrance of the exposure meter, without light losses. In the presentinstance, this is accomplished by correspondingly bent or curved lightconductors. In order to solve the problem involved it is furthernecessary that the height of the adapter corresponds approximately tothe thickness of the expo sure meter housing for design reasons since alarger distance between the measuring plane and the plane of the paperof the easel would automatically cause a measuring error in view of theincrease of the luminous intensity with the square of the distance, atsmaller spacings from the light source. In this connection, the distanceof the center of the light entrance opening at the exposure meter fromthe abutment surface is predetermined.

in view of the fact that the light entrance opening at the adapter isspaced from the opening in the exposure meter, the entering pencil orbundle of light rays passes through both openings with full strengthonly if the measurement is carried out with the light entering perpendicularly, or if the opening in the adapter is smaller than that inthe exposure meter. If the light enters at an incline light is lost anderrors occur. The other possibility, viz, to make the opening at theadapter smaller, is unsuitable since a considerable light loss would beencountered. The same holds true for the application of a light diffuserin the entrance opening of the adapter. This problem can, however, besolved, by means of light conductors if the light impinges on themeasuring plane in a direction deviating from the perpendicular in themarginal zones. It has been found that the light conductors may have around or rectangular cross section and may not drop below a minimumradius of curvature p and a certain diameter or cross sectionrespectively in case transparent plastic material is used since themaximum angle under which the light enters and which may be accommodateddepend thereon. in order to assure that, up to a certain maximum angleof incidence, all light entering the opening of the light conductor istransmitted by total reflection, it is necessary that the radius ofcurvature remains p A d/a.

As shown more in detail in FIG. 4, d represents the length of the edgeof the square light conductor 17a or in which n is the index ofrefraction of the material of the light conductor and B the angle ofincidence. As a practical application with B 30 and n 1,492 (Plexiglass)and d 2m (or cross section 2 2mm.), Consequently, if the minimum radiiof curvature remain larger than 4.9mm, all light entering the lightconductor is deviated by and reaches the photoresistance 30 of theexposure meter.

When taking into consideration these conditions and the requirement thatthe total height of this dark room adapter, i.e., the distance betweenthe measuring plane and the working plane has to be as low as possible,the structure of this adapter as shown in H68. 5 and 6 is obtained.Incidentally, FIG. 5 shows once more a part of the above-describedconnecting device. The individual nine light conductors 17 which aremade from transparent (clear) plastic material have a square crosssection in the embodiment shown. The one ends of these conductors aredirected perpendicularly to the light inlet opening and are adapted tobe partially covered by a diaphragm 19 which is adjustable by means of aknurled wheel 18. A glass plate 20 protects the light conductors fromdust. A white surface 21 is provided around the light inlet opening sothat one can clearly recognize in which part of the projected image theinlet opening is located. The other end of the light conductors, whichis directed perpendicularly to the inlet opening of the exposure meteris provided with a further protecting glas plate 22. The requirement ofmaintaining the minimum radius p makes it necessary to bend the lightconductors twice, in opposite directions, in order to keep the height ofthe adapter at a minimum.

In accordance with the present invention, another adapter is suggestedwhich serves for determining the exposure time when takingmicro-photographs. If all light that fills the cross section of theeyepiece tube of a microscope is to reach the measuring opening oraperture of the exposure meter, the lens provided in the adapter has toproject an image of the opening of the objective of the microscope intothe opening of the exposure meter.

According to FIG. 7, the micro-adapter comprises a microscope tube 23which fits for instance into an eyepiece tube of a microscope. A convexlens 24 is connected to that end of tube 23 which is recessed into theadapter. The exit opening of this adapter is sealed against dust by asmall glass plate 25 and has such a size that as little light aspossible is lost along its path from lens 24 to the light inlet openingof the exposure meter. As before, the housing of the adapter is providedwith the above-described connecting device, including elements 2, 5, and6.

In conformity with the present invention, there is furthermore providedan adapter which may serve as a focussing screen scanner by means ofwhich the focussing screen image of a camera may be scanned point bypoint, in any desired manner. This has been accomplished by inserting alight conductor made from flexible glass fibers of appropriate lengthinto a housing which is similar to that of the micro-adapter of FIG. 7.The free end of this fiber optics" may be placed onto the point of thefocussing screen to be measured, by means of a handle in the form of asleeve. The scanned section of the image is directed into the inlet lensof the exposure meter through the flexible light conductor. It is notnecessary to employ an expensive fiber optics" in which the fibers arearranged in orderly fashion, for obtaining a correct reproduction of theimage, since an optical reproduction is not required. For the presentpurpose the transmission of the light by means of a fiber optics withunoriented fibers (light conductor) is sufficient. The employment ofsuch an arrangement yields considerable advantages over the heretoforeknown measuring methods. Among these are: only a very small section ofthe picture or image is scanned at a time and the scanning end of thefiber optics is small and can be handled easily.

The focussing screen scanner is shown in FIG. 8. It comprises a housing1 which serves for holding the fiber optics 26. The fiber optics properis provided with a handle 27 in the form of a sleeve. By means of thisflexible light conductor it is possible to scan the focussing screenimage of a camera for all practical purposes point by point.

FIG. 9 illustrates an adapter which transforms the main or basic deviceof FIG. 1 into an illumination meter. This adapter likewise comprises ahousing 1 with the previously described connecting means 2, 5 and 6. Thetop of the housing has inserted therein a rectangular plane alabaster ormilk glass disc 28. In this way, in combination with the main measuringdevice 3 an illumination meter has been created which may be employedfor instance for measuring the light intensity of work places.

FIG. 10 shows an adapter for determining the color temperature" in colorphotography. Housing 1 has its top provided with a light inlet opening29 including a glass disc 30. A slide with a red and blue filter 31 and32 is arranged in the path of light from inlet opening 29 to outletopening 290. A neutral wedge 33 is connected to one of the filter discs.The slide is furthermore provided with a manually operable indicator 34which is displaceable along a scale 35 having color temperature" valuesindicated thereon.

For purposes of determining the color temperature," or which adapters orfront filters are required, in a manner known per se, the filter slideis first adjusted in such a way that only the red filter 31 is arrangedin the path of the light rays. The deviation of the needle of theexposure meter 3 (not shown in FIG. 10) is determined. Thereafter theslide is displaced until the blue filter 32 together with the neutralwedge filter 33 produces the same deviation of the needle. The amount ofthe displacement of the neutral wedge is a measure for theblue-red-portion, i.e., for the color temperature. Subsequently, thecolor temperature can be read on scale 35.

Densitometric measurements can be carried out with an adapter accordingto FIG. 11. For this purpose, the negative to be examined is insertedinto a slot 36 of the adapter housing 1. During the inserting movementit will extend into the path of light rays of a small incandescent lamp37 which, through the intervention of a key 38 is connected to a battery39 and thereby emits light onto the light sensitive element 3c ofexposure meter 3 (FIG. 1) when the adapter is attached to the latter. Itis possible, from the number of gray shadings which are readable at theexposure meter 3, to determine the greatest and smallest density valuesof the negative, i.e., the contrast of the negative. In this way, it maybe predetermined whether a hard or soft paper is to be used for anenlargement or for a copy.

While in some of the figures of the drawing the adapters have been shownby themselves, it is to be understood that each of them has to beconnected to the main measuring device 3 as shown in FIG. 1 to formtherewith a complete, operable unit.

Although the invention has been described with reference to specificembodiments thereof, it is not intended to limit the invention to suchspecific embodiments alone, but it should be interpreted in the scope ofthe appended claims.

What is claimed is 1. A light measuring device for phototechnicalmeasurements comprising in combination an exposure meter and anauxiliary device for modifying light to be applied to said exposuremeter, said exposure meter having a light entrance aperture on onesurface thereof, an extension surrounding said one surface and formingrecesses adjacent opposite sides of said one surface, and a diffuserslidably mounted with respect to said one surface whereby said diffusermay be moved into and out of alignment with said light entranceaperture, said auxiliary device having a bottom surface that conforms tothe extension of said exposure meter, a fixed protrusion extending fromthe bottom surface and for engaging a first one of the recesses in saidextension, and a movable protrusion for engaging a second one of saidrecesses opposite said first one of the recesses for holding said bottomsurface of said auxiliary device against said extension of said exposuremeter, said auxiliary device further having an aperture aligned withsaid light entrance aperture, manually actuatable resilient means urgingsaid movable protrusion into said second one of the recessed forinterconnecting said exposure meter and auxiliary device, actuatingmeans for moving said movable protrusion against the thrust of saidresilient means for detaching said auxiliary device upon actuation ofsaid actuating means, said auxiliary device further having a recessformed therein out of alignment with said light entrance aperture andconforming to the shape of said diffuser, whereby said auxiliary devicemay be mounted on said exposure meter only when said diffuser is alignedwith the recess in the bottom of said auxiliary device.

2. The light measuring device of claim 1 wherein said first and secondrecesses are comtituted by opposed parts of a recess in the extensionsurrounding said one surface of said exposure meter and extending aroundthe circumference of said one surface, thereby to constitute guide meansfor guiding the movement of said diffuser into and out of alignment withsaid light entrance aperture.

3. The light measuring device of claim I wherein said diffuser is domeshaped and extends from said one surface beyond said extension, wherebysaid first and second recesses in the bottom of said auxiliary measuringdevice hold said diffuser out of alignment with said light entranceaperture when said auxiliary measuring device is mounted on saidexposure meter.

1. A light measuring device for phototechnical measurements comprising in combination an exposure meter and an auxiliary device for modifying light to be applied to said exposure meter, said exposure meter having a light entrance aperture on one surface thereof, an extension surrounding said one surface and forming recesses adjacent opposite sides of said one surface, and a diffuser slidably mounted with respect to said one surface whereby said diffuser may be moved into and out of alignment with said light entrance aperture, said auxiliary device having a bottom surface that conforms to the extension of said exposure meter, a fixed protrusion extending from the bottom surface and for engaging a first one of the recesses in said extension, and a movable protrusion for engaging a second one of said recesses opposite said first one of the recesses for holding said bottom surface of said auxiliary device against said extension of said exposure meter, said auxiliary device further having an aperture aligned with said light entrance aperture, manually actuatable resilient means urging said movable protrusion into said second one of the recessed for interconnecting said exposure meter and auxiliary device, actuating means for moving said movable protrusion against the thrust of said resilient means for detaching said auxiliary device upon actuation of said actuating means, said auxiliary device further having a recess formed therein out of alignment with said light entrance aperture and conforming to the shape of said diffuser, whereby said auxiliary device may be mounted on said exposure meter only when said diffuser is aligned with the recess in the bottom of said auxiliary device.
 2. The light measuring device of claim 1 wherein said first and second recesses are constituted by opposed parts of a recess in the extension surrounding said one surface of said exposure meter and extending around the circumference of said one surface, thereby to constitute guide means for guiding the movement of said diffuser into and out of alignment with said light entrance aperture.
 3. The light measuring device of claim 1 wherein said diffuser is dome shaped and extends from said one surface beyond said extension, whereby said first and second recesses in the bottom of said auxiliary measuring device hold said diffuser out of alignment with said light entrance aperture when said auxiliary measuring device is mounted on said exposure meter. 